docs: def coordinate_dimension_matrix(nc):
      '''
      Returns a dictionary of coordinates mapped to their dimensions
  
      :param netCDF4.Dataset nc: An open netCDF dataset
      '''
      retval = {}
      x = get_lon_variable(nc)
      if x:
          retval['x'] = nc.variables[x].dimensions
      y = get_lat_variable(nc)
      if y:
          retval['y'] = nc.variables[y].dimensions
  
      z = get_z_variable(nc)
      if z:
          retval['z'] = nc.variables[z].dimensions
  
      t = get_time_variable(nc)
      if t:
          retval['t'] = nc.variables[t].dimensions
      return retval